In modern communications systems (in particular the Internet) it has become desirable to measure network performance. The Internet is a major world-wide packet switched telecommunications network and is a collection of heterogeneous networks all using a set of networking protocols, otherwise known as the IP suite. The IP suite has been developed to allow cooperating computers to share resources across the network. The IP suite incorporates many other networking protocols, which all perform different tasks within a network, such as UDP (User Datagram Protocol), ICMP (Internet Control Message Protocol), ARP (Address Resolution Protocol) and RTP (Real Time Protocol).
A number of working groups within IETF (Internet Engineering-Task Force) do standardization work on TCP/IP and related protocols, which are documented in “Requests for Comments” (RFCs).
There are many Internet Service Providers (ISPs) that provide access to Internet-based services for their business and residential customers and the number of users and the size of the networks is increasing rapidly. This recent rapid expansion looks set to continue and evolving commercial services e.g. on-line shopping, and new technologies such as ×DSL and 3G, which provide speech and video services, will further increase the pressure on ISPs to provide better services and service guarantees.
ISPs use traffic engineering to make efficient usage of available network resources and it has become a common desire to measure network performance in order for the ISPs to meet pre-defined Quality of Service (QoS) and Service Level Agreements (SLA's) with their customers.
Currently known technologies are not adequately suited to the task of measuring the performance of modern telecommunications networks, such as the Internet. This is because the protocols currently being implemented are not scalable or efficient, as they were not designed to be used to measure large scale and increasingly more complex modern networks.
Existing tools used for monitoring networks such as the Internet Control Message Protocol (ICMP) are limited in their applicability for the task of network performance monitoring. One reason for this is that routers are designed and optimized for the purpose of forwarding packets and therefore, routers are inappropriate measurement targets. In addition, tasks which require a high level of network resources are processed with a low priority, or not at all, in order to minimize or negate the effect of a malicious attack on the network, based on one of these resource intensive tasks. This has led a number of Internet service providers (ISP's) to disable the ICMP feature on their networks.
A need therefore exists for a measurement protocol for modern networks which is efficient and scalable. An example of such a measurement protocol has already been proposed and is called the “IP measurement protocol (IPMP)”. IPMP has been disclosed in an Internet Draft by Bennett and McGregor [Network working Group, Waikato University November 2003] and may become a widely adopted Internet standard.
The principle of this protocol is to use measurement packets, or active packets, to allow routers to participate in measurement by the insertion of path information into the measurement packet as it passes between a pair of hosts, or other measurement device.
The packet size in IPMP is restricted such that it has the highest possible degree of transmission compatibility across the network. The limit placed on the packet size has the effect that at some point the packet will become unable to collect any more data from the routers as it travels on the network between two measurement devices. This limitation in the amount of data which the measurement packets can collect therefore limits the numbers of measurements that can be made of the network.
The present invention seeks to address this limitation; however the present invention is not limited to IPMP or the measurement application and could be applied in other protocols and applications. Specifically, the particular problem which the present invention seeks to address arises from the restricted byte size of the IPMP data packets.